1. Field of the Invention
The present invention relates to power management systems incorporated into electronic devices such as computers, workstations and network servers.
2. Related Art
Electronic devices are now the subject of energy conservation programs in both the United States and abroad whose goal is to reduce power consumed by such devices. Fully powered computers consume from 60 to 200 watts of power. Such programs may require the computers to limit their power consumption to about 5 watts, as a representative example. To meet the energy consumption requirements of such standards, computers and other electronic devices have begun to incorporate power management techniques. Power management balances two competing goals: First, power management conserves electrical energy while a computer is idle; second, it maintains the computer ready to respond to user requests or external events, such as incoming signaling from a network or from a telephone line. Typically, power management and control are performed by operating system ("OS") software resident within a computer. Applications, computer programs and device drivers influence decisions made by the OS.
"Devices" include disk drives, modems, monitors and other computer components that may be configured to operate at one or more power states. Typically, the power states include a fully powered state, an unpowered state and one or more intermediate power states. Although each power state defines the power consumed by the device, it also affects the device's performance.
Consider a hard disk drive as an example. Relative to other memories within a conventional personal computer, a hard disk drive is used infrequently; typically it is accessed for storage of data that is too large to fit within random access memory or for storage of data that is used infrequently. Access time, measured from the time that a computer's central processor demands data from the drive to the time the drive furnishes the data, is a key performance characteristic of hard drives. The access time ideally should be as short as possible.
Hard drives store information on platters provided within the drive. The platters spin under magnetic heads at a predetermined rate. The heads read the information from the platters. To minimize the access time, the drives typically maintain the platters spinning at the predetermined rate; however, the drive must be energized to keep the platters spinning. While it may be preferable to maintain the drive unpowered to meet the requirements of an energy conservation program, doing so greatly impairs performance of the drive by increasing its access time.
Accordingly, applications and device drivers for electronic devices must incorporate power management techniques that balance performance requirements against the requirements of energy conservation programs. The applications will interface with device drivers and an operating system provided on the computer to implement the power management techniques. And, when several applications run on a computer at once, power management techniques of one application may conflict with another.
To meet the requirements of the energy conservation programs, a computer must include a reliable power management system. However, power management decisions may be made by applications, device drivers, BIOS and the OS. Some decisions of an application, for example, may conflict with decisions made by another. Identification and debugging of such conflicts cannot be made without a diagnostic to monitor the power states of the devices and to determine when devices change power states and to determine which of the applications, device drivers, BIOS or OS cause the device to change power states.
Energy conservation programs may require periodic audits of a computer to determine whether the computer consumes power at a rate that is permitted under the program. Accordingly, there is a need in the art for a power management diagnostic that polices computers for compliance with energy management programs. There is a need in the art for such a system that monitors power consumption of specific devices within an electronic device at specified power levels.